Process for the coloration of artificially produced oxide films on aluminum and its alloys



invention. We have found that we can color such Patented Oct. 11,1938

UNITED STATES.

PATENT OFFICE PROCESSFOR THE COLORATION ARTI- FICIALLY PRODUCED OXIDEFILMS ON ALUMINUM AND ITS. ALLQYS Frederick Hill and Jack AugustusRadley, Blackley, Manchester, England, assignors to Imperial ChemicalIndustries Limited, a corporation of Great Britain No Drawing.Application January 12, 1938, Se-

i rial No. 184,710.

In Great Britain January 18,

2 Claims. (01. 148-6) The-present invention relates to methods ofcoloring artificially produced oxide filmson aluminum and its alloys,more especially to dyeing so-called anodized aluminum. I

This invention has as an object to devise a new method of dyeing suchoxide films. A further object is to produce artificial oxide filmscolored by the new process. Further objects will appear hereinafter. u ii t These objects are accomplished by the following artificial oxidefilms by treating them in a dyebath containing an ester salt of a leucovat dyestuil'. of the anthraquinone series and thereafter 15 developingthe shade by treatment with a suitable acid oxidizing agent. i

The following examples illustrate but do not limit the invention. Theparts are by weight.

Example 1 u parts of Soledon Jade Green paste as commercially supplied(see Schultz, Farbstofftabellen, 7th edition, No. 1288) are dissolved in100 parts of water, and 0.5 part of acetic acid (30%) are 25 added. Thetemperature is adjusted to 60 C.

and anodized aluminum is immersed in this dyebath for minutes. Afterrinsing the material, the color is developed by immersing for 5 minutesat ordinary temperature in a ,bath containing 1 30 part sodium nitriteandl part hydrochloric acid per 1000 parts water.

A bright green shade is obtained. 7 I

Example 2 35 In place of Soledon Jade Green of Example 1 there are taken5 parts of Boledon Brilliant Purple 2R paste as commercially supplied(see Schultz Farbstofftabellen, 7th edition, No. 1288) the procedurebeing. otherwise the same. A bright violet shade of good fastness toheat is obtained.

This invention is a valuable advance in the art as by it we can obtainshades of good tinctorial strength and fastness to light,- water andheat.

In this latter respect they are superior to any other range of dyestufisat present in this type of work and will enable aluminum products to bedyed fast to heat, such as utensils constantly in contact with hotwater, reflectors for lights, radiators and the like.

As many apparently widely different embodiments of this invention may bemade without de parting from the spirit and scope thereof, it is to beunderstood that we do not limit ourselves to the specific embodimentsthereof except as deanthraquinone series which is used in the dyebath isa dyestuif that is described under No. 1288 in Schultz,Farbstofltabellen, 7th edition, and the acid oxidizing agent which isemployed is an aqueous solution containing sodium nitrite and an acid.

FREDERICK HILL.

JACK AUGUSTUS RADLEY.

